The present invention relates in general to an assembly for heat sealing a thermoplastic heat-shrinkable plastic film and, more particularly, to a heat sealing assembly for cutting and sealing a seam in a film or layers of film without regard to the length of the seam. The infinite sealing assembly of this invention is an improvement over the conventional "L-type" sealing apparatus used in conjunction with conventional center folded-type shrink film.
With the conventional heat sealing apparatuses, such as the L-sealers used to seal a heat shrinkable plastic film around an object to be packaged, it is generally known to wrap the object to be packaged, lower the L-sealer, and cut and seal together abutting surfaces of the centerfold film.
A sealed side and one end edge of a package is thus formed by the severing and sealing of the heat shrinkable plastic film by the elevated temperature of the L-sealer blade or knife. The opposite edge is formed by the fold in the centerfold film. Excess film is cut by a heated wire or knife. The now loosely packaged object is heated to form the completed shrink wrap package.
Another drawback of the conventional sealing apparatus is a limitation of a fixed longitudinal dimension of an object that can be sealed in the centerfold film. Fixed dimensions are inherent when using an "L" type sealer, particularly the longitudinal dimension. The size of the item can be altered to some degree dependant on the particular sealing apparatus. However, there are usually limitations on the size of the item to be packaged, particularly the length of the package.
Existing sealing equipment also has a drawback related to the costs associated with capital investment and efficiency. If a package that is either longer, shorter, wider, or narrower than operating characteristics of a particular sealing machine, then another sealer is required to complete the package. Sealing equipment is expensive and may require a high volume to justify the cost of additional acquisitions of equipment.
A further drawback of existing sealing equipment is that the operating characteristics limit the film types which can be utilized with the particular sealing equipment. Equipment which satisfactorily cuts and seals a lightweight shrink wrap film may not be suitable for sealing a heavier film.
In addition, existing sealing equipment does not allow the operator to adjust the blade depth and angle to increase or decrease the dwell time of the film on the blade, thereby varying the degree of sealing of the film.